The invention relates to a call set-up method in a mobile communications system, in which method a called mobile station is checked upon routing an incoming call to see if incoming call barring is activated.
The invention further relates to a mobile communications system comprising a first subscriber register for permanent storage of subscriber data and a second subscriber register for temporary storage of subscriber data, in which subscriber data incoming call barring is set.
In the mobile communications system the incoming calls to the mobile station subscriber are routed on the basis of the location information stored in a visitor register. However, the mobile station subscriber does not necessarily always want to receive incoming calls. Then the number of calls to be routed can be restricted e.g. by using call barring or call forwarding. For example in the GSM mobile communications system the subscriber can prevent the connecting of incoming calls when the mobile station is located outside its home network, or the connecting of all incoming calls. The closed user group also determined for a mobile communications system restricts the connecting of incoming calls. Only calls between subscribers within a group are allowed to the closed user group. For other subscribers the closed user group bars the routing of a call.
FIG. 1 of the accompanying drawings shows a simplified block diagram of the Pan-European GSM mobile communications system. Mobile Station MS is through a radio path connected to a Base Transceiver Station BTS, in the case shown in FIG. 1 to base station BTS1. Base Station System BSS consists of Base Station Controller BSC and base transceiver stations BTS which are controlled by BSC. Mobile Services Switching Centre MSC usually controls several base station controllers BSC. Mobile services switching centre MSC communicates with other mobile services switching centres and through Gateway Mobile Services Switching Centre GMSC the GSM network joins other networks, such as Public Switching Telephone Network PSTN, another Public Land Mobile Network PLMN, Integrated Services Digital Network ISDN or Service Centre SC. Operation and Maintenance Centre OMC observes the function of the entire system. The subscriber, data of mobile station MS are permanently stored in Home Location Register HLR of the system and temporarily stored in that particular Visitor Location Register VLR in the area of which mobile station MS happens to be located. Information about visitor location register VLR within the area of which mobile station MS is located, is updated to home location register HLR upon location updating. Mobile station MS location information is stored in visitor location register VLR with an accuracy of Location Area LA.
FIG. 2 of the accompanying drawings illustrates a normal mobile terminating call set-up in the GSM-type mobile communications system. Only the network elements that are relevant to the call set-up signalling are shown in the Figure. A call initiated by subscriber A is routed from the network of subscriber A, which can be for example a public land mobile network PLMN, an intelligent network IN or a public switching telephone network PSTN, to the gateway mobile services switching centre GMSC of the PLMN home network of subscriber B, which GMSC sends an inquiry (message 1) about the routing information to home location register HLR of subscriber B. Home location register HLR checks from the subscriber data of mobile station MS whether an incoming call barring or a user group code for restricting calls to a closed user group has been set for the mobile station. If the barring or the user group code have not been set, home location register HLR sends a roaming number request for visitor location register VLR at the location area of mobile station MS in message 2. Visitor location register VLR reserves Mobile Station Roaming Number MSRN and sends the number to home location register HLR in reply message 3. Home location register HLR sends the roaming number further to gateway mobile services switching centre GMSC that inquired about routing information in message 4. After this, gateway mobile services switching centre GMSC can on the basis of the roaming number route the call further to mobile services switching centre MSC of subscriber B using call set-up message 5. Mobile services switching centre MSC detects on the basis of mobile station roaming number MSRN that the called mobile station MS is located in the area controlled by mobile services switching centre and requests the subscriber data (message 6) of the called mobile station from visitor location register VLR. A user group code or user group codes for restricting calls to a closed user group may also have been set on visitor location register, whereby visitor location register VLR prevents during the inquiry stage of the subscriber data the further routing of the call if the user group code does not match. If the user group barring has not been set on visitor location register VLR it sends the required subscriber data to mobile services switching centre MSC in message 7. In step 8 a normal mobile station MS page and a call set-up are performed when mobile station MS has responded.
If the subscriber data stored in home location register HLR of mobile station MS comprise an incoming call barring or a user group code, that differs from the CUG interlock code transmitted in the call set-up message, a roaming number request is not sent to visitor location register VLR but the call set-up is interrupted. Home location register HLR replies to the inquiry about routing information sent by gateway mobile services switching centre GMSC (message 1 in FIG. 2) informing with message 4 in FIG. 2 that the routing of the call cannot be done. The call attempt initiated by subscriber A is aborted and an announcement about the prevention of the call set-up is sent to subscriber A. Correspondingly, if the user group barring has been set on the subscriber data of visitor location register VLR, visitor location register VLR does not send the requested subscriber data to mobile services switching centre MSC but sends a notice about the interruption of the call set-up.
A problem with said call barrings is that the barring applies to all calls irrespective of their importance. Thus, the routing of the call is interrupted also e.g. in respect of an absolutely important announcement call initiated by the intelligent network, such as a wake-up call or an announcement about the number of prepaid call minutes.
An object of the present invention is to enable a call set-up of individual subscribers A when incoming calls to subscriber B are barred.
This new type of call set-up is achieved with the method of the invention characterized by bypassing, in this method, the incoming call barring in the case of a priority call.
The mobile communications method of the invention set forth in the preamble characterized by the mobile communications system being arranged to bypass an incoming call barring in the case of a priority call.
The invention is based on the idea that individual subscribers A are provided with a bypass of call set-up barring. The priority subscriber identifier is transmitted as a supplement to the call set-up signalling of a subscriber A entitled to bypass call barring, on the basis of said identifier the barring functionality is bypassed upon call set-up and the call is routed to subscriber B.
An advantage of such a call set-up is that the barring of a call can be bypassed in respect of an important call.